Fastmail has one feature many others lack (which is hard to research unless you want/need it and have go down the rabbit hole) - scope limited login tokens for specific uses. Specifically, you can set up one for “read only IMAP” (to archive emails using scripts etc.), “SMTP only” (to send emails from scripts like backup reports etc.) and so forth. Many, if not most, other providers either don’t have it, or if they do it’s very limited like one token only with no scope control. $0.02 hth

Why is US based one of your requirements?

I’m a recent fastmail user:

Pros: First off, they put me on a 30 day trial, so had a full 30 days to try out; I would suggest trying their trial as one of your first things.

I do love that I can make so many aliases for different email things.

I do love I can add an API key to my bitwarden account to auto-generate email masks for things: https://bitwarden.com/blog/use-bitwarden-to-generate-email-aliases-with-fastmail/

Offer’s a reasonably priced family plan for up to 6 users (50 GB per user - after using Gmail from day one, including non-email storage, my Gmail is only up to 35 GB), and they have annual plan options which give you a discount over monthly for a better deal.

Has a calendar feature, and notes, for which I am putting stuff I used to text to myself, or message to my wife on discord.

Use multiple of my own domains (purchases elsewhere), and just set the nameservers to FastMail, and they handle setting up everything for modern email like DKIM, DMARC, and stuff. Though you are not obligated to purchase a domain, they have many you can choose from. They allow you to use a ton of custom domains (where as some other providers allow like 3, 10, or 30, depending on your plan).

They have an import feature from your old mail accounts. I did not try it, as I decided to start fresh. I’m trying to move away from gmail incase they lock me out someday, but my account is in good standing, and I have access to everything there as storage; just proactively moving all my important accounts over to my own domains.

I’ll put this at the end as it is a pro or con depending on your outlook: I trust FastMail to not use my data like google, and am okay with our business relationship. Because of this, I am okay with my data not being so hard locked down that FastMail is able to restore access/help users getting locked out of their accounts. For a true End-to-End encrypted option, I question if that recovery would be possible (which can be a good thing, if your purpose is protecting your data, even from warrants/court orders/subpoenas); they may have recovery keys, but what if you lost those?

Con: Found out after my trial ended, that when I email my work, my emails go to Quarantine. Our work uses Microsoft Outlook, and they have a quarantine feature that keeps stuff from hitting even the spam folder; my work has phishing set to ‘aggressive’, which is what is quarantining my emails. Once i passed one email through quarantine, i’m recieiving them fine now. Also if the user adds the email to their contacts list.

After looking around, this appears to be an ongoing issue with microsoft from fastmail emails. You cant email email the recipient to inform them of the quarantined email, because all emails are quarantined. Not a deal breaker, as it’s microsoft’s doing, not FastMail, but still annoying, especially if you have to tell them to add you as a contact first. May get better after your domain builds some reputation with their servers, I don’t really know yet. More of a reason for me to avoid recommending Microsoft as an email provider; quarantine is great for protecting users, but unless you have an IT person regularly checking and approving quarantined emails, it is so easy to miss legitimate emails from clients. I’ve also seen an email from my gmail account in the quarantine system, so it can catch up even big email providers.

A lot of people recommend https://tuta.com/ as a more privacy conscious option, and if I did decide to leave FastMail, they are probably what I would switch to. They do have a free email. Tuta also has family options, which can be more generous storage wise depending on your plan, but their family option appears to just be pay the full price of your plan for each user to add them to your family plan, and Tuta (at least from their pricing page), only has monthly as an option, no discounts for commitments.

For fastmail, I pay $132/year ($11/month equivalent - actually $14/month if on a monthly plan) for 50 GB for 6 users (300 GB total), For Tuta it appears to be €3/user/month for 20GB, or €8/user/month for 500 GB (so for 2 users, you are either paying €6 or €16). Ultimately I found FastMail to be a better choice for me. If you switch to business, they do have a €6/user/month option for 50 GB /user, which would be €12/month, so comparable to FastMail’s family plan if you only have 2 users, but less comparable if you need more than 2 users. Due to tuta’s pricing structure, you could just get each user the plan they need (not sure if that requires separate accounts, or if can be done on a family plan, which does have domain sharing implications, but maybe everyone wants their own domains).

My recommendation would be to make a FastMail trial, make a free tuta account, and try both for a month, then make your decision.

I think you should reconsider Proton. It seems to tick all of your boxes except US-based. However, I know they have US-based VPN servers, so I expect they have US-based email servers as well. It’s worth asking their support team about.